As an apparatus equipped with a brushless motor in a driving section, there is an electric power steering apparatus (EPS). The electric power steering apparatus is intended to apply a steering assist force (assist force) to a steering mechanism of a vehicle by a rotational force of a motor, and applies a steering assist force to a steering shaft or a rack shaft through a transmission mechanism such as gears with a driving force of a motor controlled by an electric power supplied from an inverter. Such the electric power steering apparatus in the related art accurately generates a torque of a steering assist force, and thus carries out a feedback control of a motor current. The feedback control is intended to adjust a voltage applied to the motor to reduce a difference between a steering assist command value (current command value) and a motor current detected value. Adjustment of the voltage applied to the motor is generally made by a duty adjustment in a pulse-width modulation (PWM) control, and as the motor, a brushless motor is typically used, which is superior in durability and maintainability and produces less undesired sound and noise.
To illustrate and describe a general configuration of the electric power steering apparatus in FIG. 1, a column shaft (steering shaft, handle) 2 of a steering wheel 1 is coupled to steered wheels 8L and 8R through reduction gears 3 in a reduction section, universal joints 4a and 4b, a pinion rack mechanism 5, tie rods 6a and 6b, and further through hub units 7a and 7b. The column shaft 2 is provided with a torque sensor 10 that detects a steering torque Th of the steering wheel 1 and a steering angle sensor 14 that detects a steering angle θ, and a motor 20 that assists a steering force of the steering wheel 1 is coupled to the column shaft 2 through the reduction gears 3. Power is supplied from a battery 13 to a control unit (ECU) 30 that controls the electric power steering apparatus, and at the same time, an ignition key signal is inputted into the control unit 30 through an ignition key 11. The control unit 30 calculates a current command value of an assist (steering assist) command based on the steering torque Th detected by the torque sensor 10 and a vehicle speed Ve1 detected by a vehicle speed sensor 12, and controls current supplied to the motor 20 for the EPS by a voltage control command value Vref with, for example, compensation made for the current command value.
The steering angle sensor 14 is not necessarily required and may not be disposed. The steering angle can also be obtained from a rotational sensor such as a resolver connected to the motor 20.
A Controller Area Network (CAN) 40 that sends or receives a variety of information on the vehicle is connected to the control unit 30, and the vehicle speed Ve1 can be received from the CAN 40 as well. The control unit 30 has also a Non-CAN 41 connected, which sends or recieves, for example, communications, analogue/digital signals, and radio waves other than the CAN 40.
An exemplary power transmission mechanism of the motor 20 of the electric power steering apparatus and an exemplary connection of the motor 20 with the control unit (ECU) 30 are as illustrated in FIG. 2.
As illustrated in FIG. 2, an output shaft 21 of the motor 20 is extended toward outside of a motor housing 22. The motor housing 22 that forms a motor yoke includes a bottomed, substantially cylindrical case body 23 that houses a motor body including a rotor, for example, and a motor mounting section 24 mounted on an opening side of the case body 23. The motor mounting section 24 is formed into a sheet as a whole, and via a through-hole in a central portion thereof, the output shaft 21 is inserted outside the motor mounting section 24. The motor mounting section 24 may be formed by a flange.
A power transmission mechanism 50 has a worm reduction mechanism comprising a worm 51 and a worm wheel 52 and further includes a connecting portion 53 that connects the worm reduction mechanism and the output shaft 21. The worm 51 is formed in a middle part of a worm shaft 51A that is coaxial with the output shaft 21, and is engaged with the worm wheel 52. An upper (steering wheel) side output shaft 2A of the column shaft 2 that integrally rotates with the worm wheel 52 is connected to a shaft center of the worm wheel 52. By the worm reduction mechanism, the rotation of the motor 20, that is, the rotation of the output shaft 21 is reduced and transmitted to the upper side output shaft 2A.
An internal space of a motor mounting section 54 on a side of the reduction mechanism is formed into a trumpet shape so as to expand on a side of the motor 20 (opening side), and an opening of the motor mounting section 54 is closed by bolting the motor mounting section 54 to the motor mounting section 24 on the side of the motor 20. In a condition illustrated in FIG. 2 where the motor 20 is mounted on the motor mounting section 54, the connecting portion 53 and the output shaft 21 are positioned at a shaft center of the internal space of the motor mounting section 54. Ina case where the motor mounting section 24 is formed by a flange, the motor mounting section 54 is, in response to this, formed by a flange as well.
The motor 20, and the control unit (ECU) 30 or an ECU substrate are separated from each other and wired by a lead wire 31, and the motor 20 is drive-controlled by the control unit (ECU) 30 through the lead wire 31.
In this type of the electric power steering apparatus, it is requested to reduce an overall weight and size including the motor, and it is also strongly desired to improve assemblability and axial precision of the motor.
A motor housing that can reduce part assembly work while maintaining insulation among power supply members and simplifies a power supply structure from an external power source to a motor is disclosed in, for example, Japanese Published Unexamined Paten Application No.2008-160988 A (Patent Document 1). A motor insulating housing 60 disclosed in Patent Document 1 is, as illustrated in FIGS. 3 and 4, integrally formed with a housing body 65 by an insert-molding with power supply members 61 to 64 insulated, laminated, and arranged at a distance from one another in a through-thickness direction. It is disclosed that a power connector 66 that has supply terminals 61A to 63A of the power supply members 61 to 63 as connector terminals is integrally molded with the housing body 65. The power supply members 61 to 64 each are provided with a coil terminal 67 protruding outward.